jsp实现简单的文件上传与下载功能
在家闲的发慌，只能通过学习来解解闷，刚好学到jsp(虽然很多人说这个过时了，但学校却要学，拓宽一下知识面，也没什么不好…)。博客中如有哪里不对，还望大佬以留言或邮箱方式指正，邮箱地址 [email protected]
一.文件上传
- 前端jsp文件代码贴一下(虽然说极其简陋…)
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<form action="/upload" method="post" enctype="multipart/form-data">
<input type="file" name="img">
<input type="submit" value="上传">
</form>
<a href="/download?filename=2.jpg">下载</a>
</body>
</html>
- 后端Servlet 代码，用到了两个jar包（1：commons-fileupload-1.3.1.jar 2：commons-io-2.4.jar）
package com.home.lyp.servlet;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadBase;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.List;
@WebServlet(name = "UploadServlet",urlPatterns = "/upload")
public class UploadServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp){
doPost(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp){
try {
req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
// 上传
boolean flag = ServletFileUpload.isMultipartContent(req);
if (flag){
DiskFileItemFactory fileItemFactory = new DiskFileItemFactory();
ServletFileUpload servletFileUpload = new ServletFileUpload(fileItemFactory);
// 设置上传时临时缓冲区大小
fileItemFactory.setSizeThreshold(1024*2);
String pathTemp = req.getSession().getServletContext().getRealPath("uploadtemp");
// 设置上传临时目录
fileItemFactory.setRepository(new File(pathTemp));
// 控制上传文件大小
servletFileUpload.setSizeMax(1024*1024);
try {
List<FileItem> items = servletFileUpload.parseRequest(req);
for (FileItem item : items) {
// 拿网页表单name属性值
String name = item.getFieldName();
if (name.equals("img")){
//item.getString();
System.out.println(name);
// 拿上传的文件
String FileName = item.getName();
// 简单的判断拿到的文件的后缀
String ext = FileName.substring(FileName.indexOf(".")+1);
System.out.println(ext);
if(!(ext.equals("png") || ext.equals("jpg") || ext.equals("gif") || ext.equals("jpeg"))){
System.out.println("文件类型有误");
req.getRequestDispatcher("succes.jsp").forward(req,resp);
return;
}else {
// 上传路径
String path = req.getSession().getServletContext().getRealPath("upload");
File file = new File(path,FileName);
item.write(file);
}
}
}
} catch (FileUploadBase.SizeLimitExceededException e){
System.out.println("上传文件超出限制大小");
}
catch (FileUploadException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
try {
req.getRequestDispatcher("succes.jsp").forward(req,resp);
} catch (ServletException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
二，下载
package com.home.lyp.servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.net.URLEncoder;
@WebServlet(name = "DownloadServlet", urlPatterns = "/download")
public class DownloadServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req,resp);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8");
String filename = req.getParameter("filename");
// 下载文件需要设置消息头
// System.out.println(filename);
resp.addHeader("content-Type","application/octet-stream");// 二进制文件
// 解决ie下载文件名称乱码问题 URLEncoder.encode(filename,"utf-8")
resp.addHeader("content-Disposition","attachment;filename="+ URLEncoder.encode(filename,"utf-8"));
// servlet通过文件地址 将文件转化为输入流 读到servlet中
InputStream inputStream = getServletContext().getResourceAsStream("/res/"+filename);
//System.out.println(inputStream);
// 输出给用户
ServletOutputStream outputStream = resp.getOutputStream();
// 缓冲
byte[] bs = new byte[1024];
int len ;
while ((len = inputStream.read(bs))!=-1){
outputStream.write(bs,0,len);
}
inputStream.close();
outputStream.close();
}
}